About UML statechart diagrams

A state machine, which is attached to a class or use case, is a graph of states and transitions that describes the response of an object to outside stimuli.

A statechart diagram represents a state machine. By documenting events and transitions, a statechart diagram shows the sequence of states an object goes through during its life.

To represent a flow driven by internally generated actions rather than external events, use an activity diagram.

The initial state is the state of an object before any events in the diagram have acted upon it.

A state represents an instant in the life of an object. Double-click a State shape to add a name and list its internal actions and activities.

TransitionsTransitions indicate that, in response to an event, an object will go from one state to another and perform an action.

The event which triggers the transition is named in the transition string. Double-click a transition to label it with a string that, in addition to an event signature, can also include a guard condition, an action expression, and more.